1. Field of the Invention
The present invention pertains to self-blunting medical needles and, in particular, to needle assemblies in which an internal blunting component provides a flow path to the surrounding needle housing.
2. Related Art
Many accidental needle-stick wounds are sustained by healthcare workers each day. The problem is aggravated by the trend of moving treatment out of hospitals and into doctors' offices and neighborhood clinics as part of programs to reduce healthcare costs. This trend increases the number and dispersion of healthcare workers who administer injections and draw blood samples, while reducing the frequency of such injections per individual healthcare worker. As a consequence, a larger number of less experienced people are administering injections and/or taking blood samples. Although in the past an occasional serious illness such as that caused by the hepatitis B virus was sustained as a result of an accidental needle-stick wound, the problem was not considered to be a serious one until the advent of human immunodeficiency virus (HIV) and the knowledge that this virus is transmissible to healthcare workers through needle-stick wounds from a contaminated needle. HIV causes acquired immune deficiency syndrome (AIDS) which has already killed millions and infected millions more. HIV is often referred to simply as “the AIDS virus” and the Surgeon General of the United States of America noted in a published (September, 1987) interview that there is no better way to become infected with the AIDS virus than to take blood from an AIDS patient and accidentally inflict a needle-stick wound with the contaminated needle. This situation, and the rising incidence of hepatitis C, another blood-transmissible disease, has stimulated activity to develop devices which reduce or eliminate the possibility of accidental needle-stick wounds without excessively increasing the unit cost of needles.
In some prior art bluntable needle assemblies, the blunting member is open to fluid flow into a fluid chamber (e.g., a flash chamber) of the needle component by virtue of perforations in the blunting member, while the end of the blunting member is scaled off within a shuttle structure which is accessible externally of the needle component. For example, U.S. Pat. No. 5,817,060 to Overton et al, issued Oct. 6, 1998 and entitled “Unidirectional Blunting Apparatus For Hypodermic Needles”, discloses a blunting apparatus for hypodermic needles. As seen in FIG. 5, the needle cannula 26 is mounted in a hub 32 which defines a fluid chamber (bore 34). The blunting member 40 extends into the cannula from a shuttle (positioning member 44). The shuttle is disposed partially within the fluid chamber but it also protrudes outwards to provide a surface 50 by which the blunting member can be moved from outside the chamber. The end of the blunting member is not open for fluid flow to the chamber, so the blunting member is perforated for this purpose (apertures 48). A similar arrangement is seen in U.S. Pat. No. 5,743,882 to Luther, issued Apr. 28, 1998 and entitled “Needle Blunting Assembly For Use With Intravascular Introducers” (see FIGS. 4 and 5) and in U.S. Pat. No. 5,697,914 to Brimhall, issued Dec. 16, 1997 and entitled “Control Forward/Flashback Forward One Hand Introducer Needle and Catheter Assembly”, although in the Brimhall Patent the relative positions of the catheter (which is analogous to a blunting member) and the needle cannula are reversed (see FIG. 2).
In other prior art assemblies, the end of the blunting member is open to fluid flow into the needle component chamber, but the shuttle is wholly enclosed within the needle component. For example, the Bio-Plexus, Inc. Patent to Burzynski et al, U.S. Pat. No. 5,951,520, issued Sep. 14, 1999 and entitled “Self-Blunting Needle Medical Devices And Methods Of Manufacture Thereof”, discloses a self-blunting needle assembly in which the needle component defines a fluid chamber (within syringe body 102) and the end of the blunting component is open to fluid flow to the chamber. However, the blunting component shuttle (hub 16) does not extend outside the fluid chamber for access from outside the chamber.
In still other prior art devices, the end of the blunting member is open and fluid can flow therethrough but there is no fluid flow communication from the blunting member to a fluid chamber on the needle holder or the blunting member shuttle. This configuration is illustrated in U.S. Pat. No. 4,627,841 to Dorr, issued Dec. 9, 1986 and entitled “Infusion Needle”, where it is seen that the blunting component or “catheter” 17 is mounted in a bore in hub 12 which perforates, i.e., extends through, the hub and therefore has two open ends. Catheter 17 is disposed concentrically within needle cannula 14 and the rearward end 19 open for fluid flow. However, the needle holder (hub 11, FIG. 4) and hub 12 do not define a flash chamber and the open end of the blunting component.